Modern communications and data networks comprise nodes that enable transport of data through the network. Such nodes may include routers, switches, bridges, or combinations thereof, for conveying the individual data packets or frames through the network. Some networks may offer data services that forward data frames from one node to another node across the network without using pre-configured routes on the intermediate nodes. Other networks may forward the data frames from one node to another node across the network along pre-configured or pre-established paths. In some networks, the nodes may create Ethernet-Local Area Network (E-LAN) services, where traffic that corresponds to different services may be transported along different sub-networks (e.g., by different subsets of nodes).
Due to the demand for high speed data transport and the ability to support high-bandwidth transmission rates, many data network devices are deployed with the capability to carry out switching by Layer-2 hardware. Layer-2 switching devices may be deployed for example to alleviate switching bottlenecks within subnets of a LAN environment. Multiprotocol Label Switching (MPLS) is an Internet Engineering Task Force (IETF)-specified framework that provides for the efficient designation, routing, forwarding, and switching of traffic flows through a network. In an MPLS network, a label edge router (LER) assigns a suitable “label” to incoming packets, and the packets are forwarded along a label switch path (LSP) where label switch routers (LSRs) makes forwarding decisions based solely on the contents of the label and the port through which the packet arrived. At each hop, the LSR would strip off the existing label, and would apply a new label to inform the next hop how to forward the packet.
LSPs are established by network operators for a variety of purposes, such as to guarantee a certain level of performance, to route around network congestion, or to create tunnels for network-based virtual private networks (VPNs). An LSP can be established using MPLS that crosses multiple Layer-2 transporting systems such as ATM, Frame Relay, or Ethernet.
Hand-over in a cellular network is a well known technique in the art. It is handled in a timely manner via dynamic protocols like 3GPP, SCTP, and the like. However, no adequate solution has yet been proposed for pure L2/ MPLS-TP type of networks for carrying out handover of a moving network element (“ME”) (e.g. a train) that moves between stations.
CN101820655A for example has made an attempt to address this issue. The publication describes a method for realizing Radio Block Center (RBC) soft handoff in a train control system of the type CTCS-3. The method separates a radio communication network (GSM-R) access function in RBC and integrates the function into a device called as an RBC communication gateway, a vehicle-borne Automatic Train Protection (ATP) and the RBC communication gateway keep always-on-line circuit link, and the RBC communication gateway and related RBC are linked by adopting the manner of Ethernet plus TCP/IP. When receiving a data packet of the vehicle-borne ATP, the RBC communication gateway carries out RBC according to the ID of the RBC contained in a header and determines to which RBC the data packet should be re-transmitted. As ground link is a virtual link based on TCP, the vehicle-borne ATP can communicate with a plurality of RBCs through one link, thus achieving the RBC handoff. Unfortunately, the solution provided by this publication is not sufficient to overcome the problems at hand.